It is common to see large and unsightly blotches or patches of a white crystalline formation on the face of brick walls. These patches are formed when water moving through a wall or other structure, or water being driven out as a result of the heat of hydration as cement stone is being formed, brings salts to the surface that are not commonly bound as part of the cement stone. As the water evaporates, it leaves the salt behind, which forms a white, fluffy deposit. The resulting white deposits are referred to as “efflorescence”.
Efflorescence is a whitish deposit on the surface of material, having as its main components CaCO3, Na2CO3, K2CO3, or CaSO4 for example. The formation of efflorescence depends on the presence of water soluble salts (especially Ca2+), the presence of water and the presence of channels along which water can migrate to the surface of the material. During hydration of cement for example, water soluble chemicals such as Ca(OH)2 are formed. During drying, these water soluble chemicals migrate with water to the surface of the material and then react with the CO2 or SO2 in the air to form the respective carbonate or sulphate salt. More specifically, sulfates and carbonates being drawn from the material by the moisture leave a crystalline deposit on the surface of the material, after the evaporation of the moisture. While formed in all seasons, efflorescence is an especially serious problem in winter because of the slower hydration and the lower water solubility of chemicals at colder temperatures.
Surface efflorescence causes aesthetic detriment that can monetarily devalue afflicted masonry. Particularly, in case of dark colored mortar surfaces for example, the formation of bright spots causes an irregular pattern of high contrast. When efflorescence occurs underneath a water-repellent coating, salt crystals expand as they grow and can cause extreme pressures that can result in the spalling and flaking of a building material. This process can ultimately compromise the structural integrity of the building material.
Diluted acids and other strong active agents are used commonly to remove the efflorescence from bricks however the white patches soon reappear.
Hydrophobic additives have also been incorporated into inorganic building material in an attempt to reduce moisture penetration and reduce efflorescence. However, the addition of such additives is self-limiting since water is needed for example to hydrate the cement in order to cure the concrete. Too much hydrophobic material in the wet concrete inhibits this hydration. Furthermore, when the degree of hydrophobicity of concrete increases, the degree of suction and bonding decreases. It becomes very difficult and time consuming adjusting the amount of hydrophobic additives that is needed without being detrimental to the concrete essential properties.
Hydrophobic films have also been used to ineffectively form a physical barrier that block the passage of air, water, and water vapor on the surface of bricks or blocks for example in order to reduce efflorescence.
Accordingly, there is thus a need to be provided with a composition or method to reduce efflorescence happening on new pavers, concrete bricks, stones or concrete furniture.